Max Shatto, 3, who was adopted from Russia, lived in Texas with his adoptive parents. He reportedly died on January 21.

Russia's Foreign Ministry expressed concerns over the ruling about his death, saying it did not receive the information from U.S. officials, but from the media.

It asked the United States to provide Russian consular representatives the relevant forensic documents, including a death certificate.

"We presume that this is not a final conclusion of the investigation. Still expect from the U.S. authorities -- both Texas and federal, including the U.S. Department of State -- the most complete information on the progress and results of the inquiry," the Russian Foreign Ministry said in a statement.

A medical examiner in Ector County determined the death was caused by a laceration of a small bowel artery due to blunt trauma to the abdominal area, said District Attorney Bobby Bland.

The bruising was consistent with a "self-inflicted" injury, according to Bland.

Toxicology reports were negative and there were no substances found that could have contributed to the child's death.

The sheriff's office said it is conducting more investigations with other agencies.

The boy's death drew international attention after a Russian government child advocate said that the boy was "killed" or "murdered."

At a news conference last week, Children's Rights Commissioner Pavel Astakhov said he tweeted those words based on the initial reports he received about the death. He acknowledged he may have spoken too soon.

Still, he wants his country to ban all international adoptions of Russian children.

That law bans adoptions by Americans ostensibly because of documented cases of abuse by adoptive parents. But others say the Russian move is in retaliation for a U.S. law that places restrictions on Russian human rights abusers.

Americans adopted close to 1,000 Russian children last year, according to State Department figures.

Though the number has been dropping in recent years, Russia remains the third most popular foreign country -- after China and Ethiopia -- for U.S. foreign adoptions.